Field of the Invention
The invention relates to an illumination apparatus. Particularly, the invention relates to a vehicle illumination apparatus.
Description of Related Art
Light-emitting diode (LED) headlights have been gradually applied in compliance with requirements for light-emitting efficiency, energy saving, and environmental protection. At present, the cost of the LED headlight remains high due to the needs of high-wattage LEDs and large heat sinks. Generally, in the existing LED low beam, a shielding plate is often required to form a clear cut-off line through the imaging of the lens, so as to prevent glare to the on-coming vehicle. However, the shielding plate also leads to reduction of utilization efficiency (e.g., at most 60% of the total efficiency) of the light source of the LED low beam.
U.S. Pat. No. 5,757,557 discloses an illumination apparatus that includes a lens body, and the lens body has a front surface, a curved sidewall expanding forward, and a rear cylindrical cavity. A light beam transmitted to the back is reflected by the curved sidewall to form a collimating beam. According to the patent, the cavity has a curved surface capable of performing a collimating function. U.S. Pat. No. 7,470,042 discloses a light source structure of which a light source has a light guiding portion with a high refractive index. A central portion on a front side of the light guiding portion is a round direct-emitting region, an outer side of the light guiding portion is a total reflection region, and a back surface of the light guiding portion has a semi-spherical recess portion. U.S. Pat. No. 7,128,453 discloses a light source structure of which a light-shielding member is shaped as a plate and shields parts of the light source in front of the vehicle, so as to define a bright-dark boundary of a light beam incident on the lens. U.S. Pat. No. 7,131,758 discloses a headlight structure, in which the required cut-off line is formed by adjusting angles of light sources and a light transmissive mask. U.S. Pat. No. 6,882,110 discloses a headlight structure, in which plural lamp units are employed to define different regions, so as to obtain a desired light intensity distribution.
Moreover, different types of optical lenses have also been disclosed in U.S. Patent Application Publication no. 2012057362, Taiwan R.O.C. Patent no. M434898, Japan Patent Publication no. 2006-147347, Japan Patent Publication no. 2010-135124, Taiwan R.O.C. Patent Publication no. 201139935, Taiwan R.O.C. Patent no. M310992, and Taiwan R.O.C. Patent no. 1307174.